Fumigate
by TheRealEvanSG
Summary: Vigilantes, villains, and professional heroes who aren't always heroic - Kemuri Sekai has his work cut out for him! With his cousin, Shiozaki Ibara, always there for him, though, as well as his Father's Smoke Quirk, he'll find some way to navigate all these butterflies that seem to flutter around every corner. [SI]
1. A Brand New Sekai

Chapter 1: A Brand New Sekai

~o~ ONE MONTH AFTER BIRTH ~o~

Able to see for the first time in what felt like forever, Kemuri Sekai stared up at his mother in horror.

 _Is that thing even a human_? he couldn't help but wonder as his eyes locked on what looked like a lion furry staring lovingly down at his all-too-small form. She was tall and lithe, with reddish-orange fur, beautiful and soft as velvet, running all over her body. She had a bright yellow mane in place of hair, and two fuzzy ears sticking out the top of her head. The only part that looked human at all was her face, which lacked any fur.

He shuddered as she reached out to pick him up— _why am I able to be picked up, how come I have to have such a small body, whyyy_ —and since he did not have the muscles to properly shout his disapproval, he instead cried his lungs off.

His mom flinched back in surprise. Words he could not fucking understand _whatsoever_ flowed out of her mouth, but they sounded disappointed and sad. He didn't care. The big lion furry was not picking him up if he had anything to say about it. What kind of crazy, messed up world straight from some weird Japanese dude's mind had he been reborn in? He didn't know and frankly, he didn't care.  
He missed Earth.

He missed America, even with its shitty politics.

He missed being Evan and actually knowing _what his name was_.

~o~ FOUR MONTHS AFTER BIRTH ~o~

Okay. Well. At least Sekai knew what his name was now.

Mainly because his _annoying_ mother _would not stop repeating it_.

Honestly, you'd think he was a baby or something. Oh, wait, he actually _was_ a baby despite having been fourteen just… four months prior? Five? It was hard to keep track of time, stuck in a crib for most of the time while your parents worked. That was pretty much Sekai's life. He lazed around in a crib for most of the day, dully shaking the maracas the _really wonderful_ babysitter had brought him as a present. She seemed not to like it when he shook them non-stop. He liked it when she didn't like something he did. Her eyes would flash red with annoyance.

Oh, yeah. Other things he'd learned since he'd regained his eyesight, blurry as it still was—almost _everybody_ in this weird world had some sort of power. It wasn't always a physical oddity like his mother. Sometimes it was a transformative ability, like his dad's. Sekai had nearly died a second death of shock when he witnessed wisps of smoke flow through the air behind his mother's back and then quite suddenly turn into his tall, handsome father, jumpscaring the poor woman, who'd shrieked something fierce. Sekai had (blurrily) seen his own reflection in the bathroom mirror and in the water whenever his mother and father decided he needed a bath, and he didn't have any lion fur or shit. He himself was just a normal baby with blue hair, like his dad.

Did he forget to mention that hair could apparently be any color? When Sekai had been taken out grocery shopping and meeting family members/family friends, he'd noticed a wide range of hues on people's heads.

That had been a bit of a shock, too.

 _This world is never going to stop surprising me,_ he deadpanned to himself. At least his own world had been predictable and followed the laws of physics. This one he just didn't know how to deal with.

~o~ TEN MONTHS AFTER BIRTH ~o~

Sekai regarded the other baby in front of him with suspicion.

This thing couldn't be a baby. It had to be at least one or two. Maybe three. A midget, maybe, but definitely not a baby.

It had too much hair. Too much _green_ hair.

They were at what appeared to be a family reunion. (God, Sekai hated family reunions, and no, it wasn't because he was an edgy teenager. Babies couldn't be teenagers, so suck it, internet.) All around them were people he somewhat recognized from 'field trips' prior, and people he absolutely did not recognize at all. There were all sorts; a whole litter of lion people, clearly his mother's side of the family, and then more normal people, and several, like the baby who currently sat gleefully in front of him, who had long, green hair. Hair that looked suspiciously like _vines_.

Okay, seriously, what was _up_ with this world?

And were those _actual_ vines sprouting up from this button-cute fellow baby's (possibly secret toddler's) head?

He poked the baby, who was obviously a girl, in the head. She blinked cutely at him. He blinked back. She didn't react. He poked her again. She garbled.

She was weird, he decided. And not just because yes, that was definitely vines she had for hair.

Seriously, what the hell. Sekai almost wished he was back in his mother's womb. That had been the most boring time of his life, but at least it didn't have vine-haired girls and lion-bodied people. What, did the world want him to start believing in God again or something? He'd be willing to do that if it made all the weirdness go away.

Please?

 _Please_?

The vine baby poked him square in the eye in obvious retaliation for his earlier prodding.

...He was _so_ done with this second life.

~o~ ONE AND A HALF YEARS OLD ~o~

Heroes.

Heroes existed in this world. Actual, honest-to-the-God-Kemuri-didn't-believe-in, _superheroes_. Sekai didn't know whether to be ecstatic or terrified for his life.

 _Please don't let this be some weird version of Worm, please don't let this be some weird version of Worm!_ Well, actually, looking back on it, only a handful of people actually had superpowers in that series if he remembered correctly. Not that he'd ever actually _read_ much of it, but at the very least, the general public didn't have superpowers. Here, while there appeared to be some normal people, they were absolutely _not_ the majority.

Oh, also, he had his own ability now, too. Furry powers hadn't activated, thank god; no, instead he'd apparently inherited his dad's ability to turn into smoke. He was literally Smoker from _One Piece_. He'd only discovered it when the vine-haired baby (Ibara, he reminded himself, that was what her name was) had started poking him again on a mutual vacation their families had taken together, and he'd _refused_ to be poked any longer, and then suddenly her finger was _inside his forehead_.

She'd screamed in surprise and cried for a half hour straight.

Served her right.

...Of course, she hadn't stopped poking him the next day, the little shit.

Still, she was fun to be around when her finger wasn't in Sekai's face all the time. She loved to play with anything she could get her hands on. They fiddled with those really simple jigsaw puzzles that Sekai's babysitter occasionally got him; they built big toy block towers and then _knocked them the fuck_ down; they messed about with LEGOs that Sekai's father accidentally stepped on afterward. Fun times! About as much fun as a one-year-old midget could have, anyway. (Sekai missed video games.)

They were both slowly starting to learn how to talk. Ibara picked up on the language, which Sekai guessed was Japanese from the sound of it, faster than he did. The blue-haired boy supposed this was because his mind was hard-wired for English. Japanese and English _didn't really mix well_. He was struggling, and he could tell his parents were getting concerned. He'd already said his first word, but that had been SHIT! by accident after stubbing his toe on the side of his crib. (Don't ask.) That had earned him a strange look from his parents, and he had been exceedingly careful not to say anything in English around them after that.

...What had he been talking about before?

Oh, right. Heroes.

The first time he realized heroes existed in this strange world had been during TV time with Ibara, whose parents now brought her over to the Kemuri household twice a week. At first, he'd thought he'd been watching some kind of really-well done movie. The action sequences didn't even look planned, and that train wreck looked really real. But then he realized the TV screen looked like it was a news report. And his mother and father looked genuinely concerned. They kept glancing nervously at each other as, on screen, a masked and caped guy with extending arms and fingers rushed into and out of the burning vehicle, five people grasped in each hand. Frantic shouting came from the other side of the TV. He could only pick up some of the words, but the tone of the speakers' voices sounded genuinely afraid and concerned.

He caught the English words, "pro heroes" coming from his parents' lips.

It was the first clue Sekai had of where he was, but he didn't recognize it as such until some time from then still.

~o~ ONE YEAR AND NINE MONTHS OLD ~o~

His father, Kemuri Irori, taught him the word _Quirk_.

And quite suddenly, Sekai's entire world changed.


	2. Settling In

Chapter 2: Settling In

~o~ TWO YEARS AND FOUR MONTHS OLD ~o~

Sekai wanted to be a hero.

He was by no means alone in this desire, as he found out after attending his first day of daycare. All of the toddlers there wanted to be a hero just as badly. It was all anyone ever talked about, not that anyone could even really say much in the first place. And anyway, it would at least occupy him so he wouldn't think about...

He shuddered and forced that thought out of his mind. He would NOT think about that.

Even so, just because all the other students also shared this goal, that didn't mean his dream wasn't _his_. He wanted to be a hero and save people like the impressive figures he'd seen on TV. And unlike his classmates, including Ibara, Sekai had a plan.

He was going to get into U.A. and become the number one hero, even if he had to fight Midoriya "The Cinnamon Roll" Izuku to do so. And he was gonna start by saving Kamino Ward from All for One's future devastating attacks.

The problem was… he had no idea what kind of hero he wanted to be.

What even was a smoke Quirk good for, exactly? Well, evading attacks, obviously, if he could train himself enough to be able to turn large portions of his body into smoke. So far—and he had been experimenting—he'd only been able to transform small parts of himself. The more he trained with it, the more of himself he was able to transform, but it was a gradual increase. Unfortunately, there wasn't much about dodging things that would help with heroism.

He'd also discovered something else about his Quirk.

It had a time limit of thirty seconds, and if he surpassed that time limit, he'd start to choke on smoke that gathered in his lungs. (It didn't seem to do any harm to him other than momentarily make him unable to breathe, luckily, but the first time had still scared him badly.)

Sekai had brought it up with his father. "Daddy," he asked Irori with his best puppy-dog eyes, "why can't I use my Quirk a lot?"

Irori smiled, his boxy and smooth face making him look rugged and handsome. "Don't worry about it, rascal." Rascal was his father's pet name for him, probably because he was constantly in poke wars with Ibara. "I couldn't use my Quirk a lot when I was a kid, either. It just takes practice, and in a few years, you'll be able to turn your whole body into smoke!"

Sekai's eyes widened. "Really, Daddy?" he asked excitedly. That sounded awesome! He hadn't achieved more than a full finger so far!

The bulky man laughed and ruffled his son's blue hair. "Really, Sekai. Oh, by the way, try taking a BIIIIIG breath before you use it!"

A big breath? Sekai blinked and frowned in confusion. What did that have to do with anything?

Oh well, Irori had had the Quirk longer than Sekai. He had to know _something_ about it.

Later that day, Sekai sucked in a huge gulp of air, filling his lungs up so that his tummy popped out, and was shocked to find that he could now transform his whole arm! After some experiments, he found out that the amount of himself that changed depended on how much air he had in his lungs. His time limit remained the same regardless of how deep a breath he took, however.

Grinning, the reincarnated boy stared at his hands excitedly.

He was going to spend as much time as possible working with these powers.

If anything, it could at least distract him from what he kept thinking about when he was alone.

~o~ THREE YEARS OLD ~o~

Sekai's Quirk training was going pretty well, he thought. His other areas of training were, too, i.e. studying for his future U.A. entrance exam (albeit less so than the others) and training in martial arts.

Every day, he spent at least an hour working on how much and how long he could use his Quirk for. He'd managed to increase his time limit by two seconds. It was incredibly slow progress, but he found that the more he went over his time limit, the more he could resist the onset of smoke inhalation. Also, the more he pushed the use of his Quirk, the more of his body he was able to transform.

He'd also gotten some kids' books from the library about heroes and heroism. Since he'd finally learned Japanese decently well, he was at least able to read this much. He learned about some popular heroes from the country's past, as well as some more worldwide heroes. It wasn't very extensive other than pieces of information like that (it was meant for kids, after all), but it was better than nothing.

More helpful than his studies was his martial arts training. His body hadn't been incredibly naturally strong, much like his old one, and it was annoying going to classes every day. But it definitely paid off. He found himself slowly growing more and more limber, as well as his muscles becoming a little more defined. It wasn't anything like what he'd get if he'd chosen to lift weights (fuck _that_ noise), but it was at least something! And the best part was that it gave him self-defense skills. He quickly became the best in his class, and although that was definitely because his older brain was more able to focus and comprehend larger amounts of more complicated instructions than his classmates', he still felt much more confident in his ability to fight than before he'd started.

It wasn't a lot still, but it was tons better than nothing.

Maybe this time around, he could actually protect his life when faced with danger instead of dying.

~o~ THREE YEARS AND ONE-AND-A-HALF MONTHS OLD ~o~

" _Man, fuck that Professor James. Did you hear what he said to that poor girl, Evan? It's not like it was her fault she was late, either. Her friend told me later that she got into some kind of traffic trouble that was the other dude's fault and they both got pulled over by the cop who happened to be there."_

 _Evan Gamble, five-foot-eleven with fair skin and creamy chocolate hair, turned from his homework to wince at his friend. "Yeesh, that sucks. I'd always thought the dude was a good teacher, too. Guess some people are just really shitty, huh?"_

" _I guess so," his buddy grumbled. He ran a hand through thick red hair. "This backwater town seems like it's getting more and more fucked up daily, you know? Ol' Dave from sixth grade—you remember, him, right? The little Jehovah's Witness kid who always quoted scripture at everyone like some kind of mini apologist? Well, he goes to this damned college now, too, and is actually atheist, believe it or not, and we were talking about the whole God thing a while back. But anyway, so he texts me the other day, and what does he say? He says that he heard some guy ranting about shooting up this place!"_

" _What!?" the brunette boy stood up straight in his seat in the student commons center of his local college. "Did he call the cops? Tell me he did, Josh."_

 _Josh snorted. "You think_ Davey _has the guts to call the cops on someone? No way, man, that kid has less balls than a Flat Earth convention. He hasn't even told his mom and pop he doesn't believe in their magical sky daddy. Besides, the dude he was talking about doesn't seem like the kind of guy you'd expect to mow down a uni. I took a look at his Facebook (it's open to the public) and that boi is skuh-_ weeky _clean. Doesn't even have a hunting pic on it."_

 _Evan stared, though a little less concerned than he had been earlier. "Still, school shootings aren't a fucking joke, dude. Somebody should definitely say something."_

 _Josh shrugged and munched on a Subway sub. It was his favorite kinda club, add bacon, stacked with lettuce, cucumbers, onions, and vinaigrette. Evan called it rabbit's food. "Whatever, dude," he groaned with a mouthful of lettuce. "Something you've gotta learn about this here neck o' the woods—people here talk shit and are shitty, but are also dweebs who wouldn't know how to punch a hole through any-fuckin'-thing. Ain't nothing's gonna happen, trust me."_

 _Evan bit his lip but didn't bother to point out that Josh was hardly the kind of fellow who one should trust on predictions. He'd once claimed that he was sure their freshman science teacher was Q. And that their school nurse had been The Doctor. And he hadn't been joking, either._

 _Evan only really hung out with Josh_ because _he was the kind of dumbass who you knew would give you endless amounts of laughter. And because they were both major nerds, but that was a bit embarrassing so. Yeah._

" _Whatever you say, moron," he decided at last, rolling his eyes and shoving Josh's shoulder hard enough that the redhead almost fell out of his chair._

 _Josh yelped in surprise, choked on his sub for a nanosecond, then smirked evilly at him. "Oh, you wanna go that route, eh? Eh? You don't know what you're messing with!" Josh shoved him back harder, causing Evan to actually topple to the floor. Josh blinked, seeming mildly surprised by his own strength. "Oh shit. Sorry dude."_

 _The brown-haired English major stared at him as he scrambled to his feet. "This. Means. War."_

 _The other students in the student commons center suddenly found a great source of amusement to distract themselves from the crushing amount of essays their professors had assigned them._

A lightning bolt from an outside storm ripped the air asunder outside Sekai's apartment, startling him awake.

His eyes felt strangely wet, as though the rain from outside also ran down his cheeks.

~o~ THREE YEARS AND THREE MONTHS OLD ~o~

Sekai trained harder.

And harder.

And harder.

He ran outside up and down the sidewalk under the guise of playing. He studied Japanese until his brain felt numb so that he could fully get on the level of the other kids. He punched the red punching bag his mom, who had been much more distant around him lately for some reason, had gotten him for Christmas until his knuckles burned red.

His breath came in short, shaky pants as his worn-out fists pounded into the bag, which dangled from the ceiling on a chain. Metallic rattling filled Sekai's ears as the bag shook with force that should not have been coming out of his barely-not-a-toddler fists.

His growing muscles ached. His legs felt weak and trembly.

Tears built up in the back of his eyes, tears he struggled to not let anyone see when he was around other people. Especially not his parents.

 _They're not my actual parents. No matter how much I try and think of them, they're not—_

 _They're my parents, they gave me new life when mine ran out, they gave me a home and food and clothes and love and—_

 _But they're Sekai's, not YOURS. You left your parents behind—_

 _I AM SEKAI—_

An unfettered howl tore out of Sekai's throat and he pulled back his fists, launching a terrible kick at the poor, innocent punching bag. Pain shot through his toes, which had connected with the bag instead of his foot, and he whimpered, stumbling back and falling on his ass due to his own imbalance.

He sat there panting, nursing his injured knuckles.

He'd tried to forget about it.

God _dammit_ , he'd tried to forget.

But he just… couldn't… get it out of his mind! No matter how hard he tried to live in the present, pretend to be Sekai, he couldn't help but remember. Remember Josh. Remember his parents. Remember Foreign Exchange. Remember writing and playing video games into the dead of the night, laughing carefree and unaware of what would come.

And then that day…

 _Stop it stop it stop it!_ Sekai begged himself, feeling sick and tired. He curled up into a ball and tried to hide from his memories. _I don't want to remember!_ _I don't I don't I don't—_

A gentle hand touched his shoulder. "Kaikun?"

"...Go 'way, Ibachan," he croaked. He didn't look up from his lap.

"Are you okay?" His cousin sounded worried. He felt even worse. God, he was such a mess, now he was even making his little cousin ( _Sekai's little cousin_ ) worry about him.

"'M fine," he mumbled ashamedly. "Why are you here?"

He could feel Ibara's blush radiating even without looking. "I wanted to talk with you. You look lonely and I'm your friend. And my mom said that Jesus said to always make people happy."

He frowned bitterly into his lap. "Jesus said that, huh?" he mumbled in English. Yeah, right. He'd stopped believing after getting out of high school, and dying hadn't exactly convinced him of the Great Lord Above's existence.

"Yeah!" Ibara chirped, obviously pleased to latch onto a subject she felt happy with. "Jesus is awesome! Mom says he was the first hero! We go to… to… to this _real big building_ and learn about him a lot! Do you and your mommy and your daddy do that too?"

He slowly lifted his head up and turned to look at her. The vine-haired girl's eyes were shining with interest and excitement, and Sekai smiled to himself. Man, it was like looking at a Horikoshi child sketch come to life— _way_ too cute. "My mommy does," he answered softly, blinking away the salty water clinging to the bottom of his eyes. "My daddy and I don't. My daddy said…" He searched for the Japanese name for several seconds. "...God isn't real. They fought a lot after that."

Ibara looked horrified, like someone had just told her the world was about to end. " _Whaaaaat_?" she gasped, eyes wide as dinner plates. "Why did he say that!?" She leaned forward, desperate to know why Irori didn't believe. "Why why why?"

"I don't know," Sekai said, completely truthfully. "He started saying a bunch of big words I didn't understand. It was confusing."

"Hrmmmmm." Ibara crossed her arms and hummed suspiciously. She frowned deeply. "Well that's just mean!"

Sekai blinked. "Huh?"

"Saying someone isn't real is just mean!" Ibara said, nodding firmly and pouting. She pointed sharply at him. "Do you think he's real, Kaikun?"

Sekai stared. "I said I don't know."

"WHAAAAAAAAT!?" The poor vine-haired girl's eyes bulged out. "KAIKUN! Why why why why why!?"

He couldn't help it. Despite everything, a smile spread up his lips at the poor girl's crestfallen questioning, and he giggled, then burst into laughter. Ibara startled, then straightened up and pouted again. "Why are you laughing at me?"

Sekai smirked and booped her in the forehead. "Because you're funny."

"I'm not!" Ibara insisted. "I'm serious!" And Sekai descended into a fit of laughter again, much to his cousin's chagrin. She hummed with displeasure, but then paused and smiled. "You don't look lonely now!"

The suddenness of the statement made Sekai stop laughing. "Huh?"

"You looked so lonely… like you were here and not here…" Ibara said sadly, then brightened. "But now you're happy! I like you being happy!"

Sekai stared down at himself, opening up his hands as though expecting to find his melancholy in them. "I… guess I am," he said softly, turning his gaze back up to that little ray of sunshine he called his cousin. He hadn't even noticed when he'd stopped thinking about everything, but somewhere during the conversation, he had.

Ibara gazed at him for a moment. After a long pause, she declared, "I'm coming over every single day!"

"What!? You can't say that on your own!"

"I can too! And my mommy will let me!"

"That's not the… that's not the… uhh…" Unable to figure out the translation, Sekai settled for just pouting and folding his arms much like Ibara had done earlier. "Fine…" he grumbled, looking to the side, although not as put out as he let on.

"Yay!" Ibara cheered, hopping and then wrapping him up in a very warm hug. "I won't let you be lonely again, Kaikun! Promise!"

He didn't say anything for several moments. Then he looked up at Ibara with a soft smile and held out his pinky. "Pinky promise?"

Ibara blinked, then nodded excitedly and held out her own pinky. "Pinky promise!" she announced to the world.

As their pinkies wrapped around each other, Sekai decided that maybe it didn't matter whether he was Evan or Sekai. Not when both had things they loved in this crazy, messed up world.

...That was when Ibara noticed his red knuckles.

Her eyes widened with worry. "AAAAAH! KAIKUN, YOU HAVE A BOO-BOO!"

"Ibachan, don't tou— _owowowow_!"


End file.
